1. Field of the Invention
This invention relates generally to an optical device for controlling a light beam by means of an optical element, such as, a lens, and more particularly is directed to such a device which is capable of controlling movements of the optical element in two directions at right angles to each other so as to be particularly suited for use in an optical scanning assembly of an optical disc player or other apparatus in which a light beam is directed against a record medium surface for optically reading information recorded in a track on such surface.
2. Description of the Prior Art
It is known to provide an optical disc player with a focusing servo by which a light beam from a laser light source is correctly focused on a disc surface through an objective lens, and also with a tracking servo by which the point of impingement of the focused light beam on the disc surface is made to coincide with the track being scanned or read. In one known form of such optical disc player, for example, as disclosed in U.S. Pat. No. 4,135,083, an objective lens holder is supported by first and second sets of springs so that the objective lens can be moved, in response to electromagnetically applied forces, both in the axial direction for correcting focusing errors, and in a direction extending radially in respect to a track being scanned on a record disc for correcting tracking errors. However, the use of resilient plates or springs to support the objective lens holder, as aforesaid, gives rise to problems in that mechanical resonance of the springs or resilient plates occurs at a specific frequency and causes deterioration of either the focusing servo control or the tracking servo control. Furthermore, the use of a number of springs to support the objective lens results in a rather complex structure which is difficult to assemble and align.